1. Field of the Invention
The present invention relates to a novel compatibilizing agent for compatibilizing a radical polymerizable unsaturated resin with a polymer containing styrene as a principal component, a radical polymerizable resin composition, a molding material, and a molded article. More particularly, the present invention provides a means for solving problems of storage and molding caused by poor compatibility by improving the compatibility of the radical polymerizable resin with the polymer containing styrene as a principal component. The present invention also provides a compatibilizing agent which makes it possible to convert the resin mixture into a homogeneous resin mixture free from separation and to attain a highly value-added product.
2. Description of the Related Art
Radical polymerizable unsaturated resins are suitably used as raw resins for molding materials. However, molding materials using radical polymerizable unsaturated resin have large problems in which volume reduction, which occurs on curing, causes warpage and cracks in the molded article. For the purpose of overcoming this problem, various thermoplastic resins, for example, low profile additives such as polystyrene, styrene-butadiene rubber and the like are used. However, since these low profile additives have poor compatibility with the radical polymerizable unsaturated resin and separation after mixing is unavoidable, the resin mixture does not convert well into a homogeneous resin mixture free from separation because of its poor separation stability. Therefore, separation of the mixed low profile additive caused various molding defects such as scumming, segregation and the like.
Thus, a method of adding a stabilizer as a third component is employed and U.S. Pat. No. 3,836,600 discloses an example where a styrene-ethylene oxide block copolymer prepared by a living anionic polymerization method is used as the stabilizer. This stabilizer exerts a high compatibilizing effect and can maintain a stable dispersion state for a long period of time. However, it is difficult to industrially produce the compatibilizing agent because of its special synthesis procedure.
On the other hand, Japanese Unexamined Patent Application, First Publication No. Hei 3-174424 and Japanese Unexamined Patent Application, First Publication No. Hei 11-92646 disclose a method of improving the compatibility by introducing a vinyl acetate block or a functional group into a low profile additive. These improved low profile additives have an effect of retarding the time required to separate, but a stable dispersion state is still to be obtained by essentially improving the compatibility.